Inductive detection of 4.5 μm superparamagnetic beads in a microfluidic device

An inductance sensor based on a microwave interferometer capable of detecting magnetic markers in a microfluidic suspension is presented. The sensor can continuously detect micron-size superparamagnetic beads suspended in a microfluidic channel as they pass over a planar electrode loop. An estimated resolution of 1fH/√(Hz) was achieved, which is close to single particle resolution. The system relies solely on electronic detection, which enables it to be integrated onto an inexpensive and small-scale lab-on-a-chip platform.